code: def test_fit_transform_HaveHandleUnknownValueAndUnseenValues_ExpectAllZeroes(
      self,
  ):
      train = pd.DataFrame({"city": ["Chicago", "Seattle"]})
      test = pd.DataFrame({"city": ["Chicago", "Detroit"]})
      expected_result = pd.DataFrame(
          {"city_1": [1, 0], "city_2": [0, 0]},
          columns=["city_1", "city_2"],
      )
  
      enc = encoders.OneHotEncoder(handle_unknown="value")
      result = enc.fit(train).transform(test)
  
      pd.testing.assert_frame_equal(expected_result, result)
  
imports: import pandas
  from unittest import TestCase
  import numpy
  import tests.helpers
  import category_encoders
label_desc: Use image node_id 6 for calling the TestOneHotEncoderTestCase obj's underlying member method code with example usage: obj.test_fit_transform_HaveHandleUnknownValueAndUnseenValues_ExpectAllZeroes() without return types